The Chancellor and the Business Secretary have summoned the chief executives of the big lending banks for a summit meeting before Christmas to try to extract the long-planned deal to use surplus cash to lend to small businesses.

Their renewed drive came as Prime Minister David Cameron used a press conference at the EU summit in Brussels on Friday to warn banks that they faced higher taxes if they continued to pay unjustified bonuses. He stressed that banks must look at the political context of paying huge bonuses while the rest of the country suffered cuts.

The meeting, the exact time for which has not yet been confirmed, follows the publication of the City's revised pay rules, which will allow most City institutions to opt out of strict European rules.

The Financial Services Authority (FSA) said it had updated its Remuneration Code to take into account the tough rules announced last week by Committee of European Banking Supervisors (CEBS), But the regulator has also included wide exemptions that are open to many firms.

The FSA pledged that a "proportionate approach will be applied to implementation of the Code", which will allow hedge funds and asset managers to opt out of the rules.

Jonathan Master, partner at international law firm Eversheds, said: "Asset management firms will be able to breathe a sigh of relief that the FSA's final rules give a lot more clarity and comfort around the question of a proportionate application of some of the more prescriptive rules relating to remuneration structures."

The big banks, which will have to comply with the rules, were ready for most of the changes. However, many were shocked by the FSA's decision to extend the ban on guaranteed bonuses and retention payments from the highest paid bankers to all staff.

The FSA said: "Provisions on guaranteed bonuses should be applied on a firm-wide basis and not just to 'Code staff'."

One investment bank boss said: "This will make British banks terribly vulnerable to poaching from rival banks. If another bank tries to hire our staff, we won't be allowed to match the offer. And this will be applied to operations around the world, too. We are very concerned."

The other main change adopted by the FSA to reflect the CEBS proposals was a radical increase in the proportion of deferred pay.

CEBS proposed at least 70pc of total remuneration in financial services firms should be deferred, with the cash element being limited to a maximum of between 20pc and 30pc. The Government's new 50pc higher rate of tax could have effectively reduced the cash payment to just 10pc of the original amount.

The regulator has also adopted the European view that the deferred pay must be retained. The part of a package paid in shares, or any other instrument, must be withheld for an "appropriate retention period".

London-based banks will have to adopt the new Code by January 1, 2011. Other firms currently outside the FSA's code have until July 31, 2011, at the latest to comply.